Endometriosis and Cancer: What’s the Link?

"It’s not cause for marked alarm,” says Heather Hilkowitz, MD, of Hilltop Obstetrics and Gynecology. “The incidence is very low.”

However, this doesn’t mean that you’re off the hook.

Early treatment is your best shot at managing the disease and preventing the onset of cancer.

“Women with endometriosis do not have an overall increased risk of endometrial cancer, but some studies indicate that they may have a higher incidence of ovarian cancer,” says Michael Guy, MD, with Premier Gynecologic Oncology. One study published in the journal Human Reproduction found that endometriosis increased the risk of developing ovarian cancer by more than a third (37 percent) above the risk for women without endometriosis. Endometriosis also increases the risk of other cancers, including endocrine, kidney and thyroid, the study found.

In reality, endometrial cancer is more likely to occur if you have a different medical condition that also affects the uterine lining — endometrial hyperplasia.

What’s the Difference?

Endometriosis is a medical condition where tissue that normally lines the uterus (the endometrium) grows where it doesn’t belong — outside the uterus, often on the ovaries, fallopian tubes and other pelvic structures.

Endometrial hyperplasia occurs when the cells in the uterine lining grow rapidly and/or excessively, but unlike with endometriosis, the lining stays inside the uterus. Mild or simple hyperplasia, the most common type, has a very small risk of becoming cancerous. It may go away on its own or after treatment with hormone therapy.

However, if the hyperplasia is called “atypical,” it has a higher chance of becoming a cancer. According to the American Cancer Society (ACS), simple atypical hyperplasia turns into cancer in about eight percent of cases if it’s not treated. Complex atypical hyperplasia has a risk of becoming cancerous in up to 29 percent of cases if untreated, the ACS reports.

Keeping Cancer at Bay

When the cells of the endometrium start to grow out of control and become abnormal, as happens with hyperplasia, they could become cancerous, leading to endometrial cancer.

“That’s why it’s important to assertively treat hyperplasia,” says Dr. Hilkowitz. “Don’t just sit on this. A lot can be done to lower the risk. Hormone therapy and surgery can manage the disease and lower the risk of cancer. Birth control pills are especially powerful in preventing hyperplasia and lowering the risk of endometrial cancer.”

There is a more aggressive subtype of endometrial cancer which may be linked to endometriosis, but more research needs to be done in this area, the doctors advise.

Dr. Guy recommends discussing treatment for either of these conditions as early as possible with your physician. “Early treatment is your best shot at managing the disease and preventing the onset of cancer,” he says.